Engineering topics

Maeda, Yoshitomo

Publications and source records attributed to Maeda, Yoshitomo.

21 records · Page 2

NASA NTRS2016

The ASTRO-H SXT Performance to the Large Off-Set Angles

The X-ray astronomy satellite ASTRO-H, which is the 6th Japanese X-ray astronomy satellite and is renamed Hitomi after launch, is designed to observe celestial X-ray objects in a wide energy band from a few hundred eV to 600 keV. The Soft X-ray Telescopes (SXTs) onboard ASTRO-H play a role of collecting and imaging X-rays up to approximately 12 keV. Although the field of view of the SXT is approximately 15' (FWHM), due to the thin-foil-nested Wolter-I type optics adopted in the SXTs, X-rays out of the field of view can reach the focal plane without experiencing a normal double reflection. This component is referred to as 'stray light'. Owing to investigation of the stray light so far, 'secondary reflection' is now identified as the main component of the stray light, which is composed of X-rays reflected only by secondary reflectors. In order to cut the secondary reflections, a 'pre-collimator' is equipped on top of the SXTs. However, we cannot cut all the stray lights with the pre-collimator in some off-axis angle domain. In this study, we measure the brightness of the stray light of the SXTs at some representative off-axis angles by using the ISAS X-ray beam line. ASTRO-H is equipped with two modules of the SXT; one is for the Soft X-ray Spectrometer (SXS), an X-ray calorimeter, and the other is for the Soft X-ray Imager (SXI), an X-ray CCD camera. These SXT modules are called SXT-S and SXT-I, respectively. Of the two detector systems, the SXI has a large field of view, a square with 38' on a side. To cope with this, we have made a mosaic mapping of the stray light at a representative off-axis angle of 30' in the X-ray beam line at the Institute of Space and Astronautical Science. The effective area of the brightest secondary reflection is found of order approximately 0.1% of the on-axis effective area at the energy of 1.49 keV. The other components are not so bright (less than 5 x 10(exp -4) times smaller than the on-axis effective area). On the other hand, we have found that the effective area of the stray light in the SXS field of view (approximately 3' x 3') at large off-axis angles (greater than 15') are approximately 1(exp -4) times smaller than the on-axis effective area (approximately 590 sq cm at 1.49 keV).

X-rays↗

NASA NTRS2016

Point Spread Function of ASTRO-H Soft X-Ray Telescope (SXT)

ASTRO-H (Hitomi) satellite equips two Soft X-ray Telescopes (SXTs), one of which (SXT-S) is coupled to Soft-X-ray Spectrometer (SXS) while the other (SXT-I) is coupled to Soft X-ray Imager (SXI). Although SXTs are lightweight of approximately 42 kgmodule1 and have large on-axis effective area (EA) of approximately 450 cm(exp 2) at 4.5 keV module(sub 1) by themselves, their angular resolutions are moderate approximately 1.2 arcmin in half power diameter. The amount of contamination into the SXS FOV (3.05 times 3.05 arcmin(exp 2) from nearby sources was measured in the ground-based calibration at the beamline in Institute of Space and Astronautical Science. The contamination at 4.5 keV were measured with sources distant from the SXS center by one width of the FOV in perpendicular and diagonal directions, that is, 3 and 4.5 arcmin-off, respectively. The average EA of the contamination in the four directions with the 3 and 4.5 arcmin-off were measured to be 2 and 0.6% of the on-axis EA of 412 cm (exp) for the SXS FOV, respectively. The contamination from a source distant by two FOV widths in a diagonal direction, that is, 8.6 arcmin-off was measured to be 0.1% of the on-axis at 4.5 keV. The contamination amounts were also measured at 1.5 keV and 8.0 keV which indicated that the ratio of the contamination EA to that of on-axis hardly depended on the source energy. The off-axis SXT-I images from 4.5 to 27 arcmin were acquired at intervals of -4.5 arcmin for the SXI FOV of 38 times 38 arcmin(exp 2). The image shrinked as the off-axis angle increased. Above 13.5 arcmin of off-angle, a stray appeared around the image center in the off-axis direction. As for the on-axis image, a ring-shaped stray appeared at the edge of SXI of approximately 18 arcmin distant from the image center.

Soft X-ray spectrometer↗

NASA NTRS2016

Reflectivity Around the Gold M-Edges of X-ray Reflector of the Soft X-Ray Telescope Onboard ASTRO-H

The X-ray astronomy satellite ASTRO-H are equipped with two equivalent soft X-ray telescopes (SXT-I and SXT-S) which cover the energy band 0.3-12 keV. The X-ray reflectors of the SXTs are coated with a gold monolayer by means of the replication technique. A series of gold M absorption edges in the 2-4 keV band causes complex structures in the energy response of the SXTs. In the same band, there are astrophysically important emission lines from Si, Ar and S. Since the SXS has unprecedentedly high spectral resolution, we have measured the reflectivity around the gold M-edges in an extremely fine energy pitch at the synchrotron radiation facility KEK PF BL11-B, with the 2 eV pitch in 2100 eV to 4100 eV band that covers the entire series of the absorption edges (M-I through M-V) at grazing incident angles to the reflectors of 0.5, 0.8, 1.0, 1.2, 1.4 degree, and with a finer pitch of 0.25 eV in the 2200 eV to 2350 eV band where the two deepest M-IV and M-V edges are included. In the resultant reflectivity curves, we have clearly identified the fine structures associated with all the M-edges. Using these data, we calculated atomic scattering factor f1 as a function of X-ray energy, with which we have built the mirror response function which can be applied to the Suzaku spectra. As a result, we have found that discrepancy of the spectral model to the Suzaku data of 4U1630-472 (a black hole transient) and the Crab nebula around the M-edges are significantly reduced from those with the official Suzaku response.

ASTRO-H↗